DIP devices and particularly the new "gull-winged" DIP devices form an important part of the electronics industry. These DIP devices are placed on a printed circuit board which has been silk screened and treated to define precise locations for the pads of the DIP device leads. Precise location of the DIP device is needed for successful manufacturing.
DIP devices are required to meet certain standards of uniformity, both in the distance between individual pins or leads and in the coplanarity of the leads which extend down from the body for attachment to the printed circuit board. For example, manufacturing standards for a particular device may call for the pads of the DIP device all to be within a range of ten thousandths to twenty thousandths of an inch. Various manufacturers and various products may have different body stand-off ranges, such as ten to twenty thousandths, or seven to twelve thousandths and the like.
Additionally, all of the leads must be within four thousandths of an inch in coplanarity of each other in order to ensure proper mounting on the PC board. The four thousandths coplanarity range is becoming an industry standard. Coplanarity inspection and adjustment is a significant need in the electronic industry.
As was mentioned above, the specifications for the distances between pins or leads is also of major concern. It has become desirable to ensure that the distance between leads is within a certain range, for example a distance of ten thousandths of an inch. Each of the many leads on the DIP device will then contact the appropriate pad on the printed circuit board. Scanning is extremely important to verify that none of the pins or leads are missing. Those DIP devices which have a missing, or widely skewed lead, need to be taken out of the automatic assembly process.
The manufacturing processes by which DIP devices are made are themselves highly automated and efficient. In some instances, less than two percent of the devices made will be out of tolerance by an amount sufficient to need straightening, either in the pin to pin direction or with respect to coplanarity of all of the leads. In other manufacturing processes, depending upon the quality and the complexity, the number of DIP devices from a given production run which needs straightening will range from as low as one percent to as high as ten percent. In most cases, the DIP devices which do not meet the initial specifications are still within a range which would permit them to be straightened or realigned. Actual rejection due to a missing lead or a badly skewed lead is extremely low. Nevertheless, it is becoming an industry standard to inspect every DIP device as part of the assembly process.
One such device which is admirably suited for lead straightening, both in the pin to pin alignment and in the common plane is disclosed in a commonly owned Linker U.S. patent application Ser. No. 565,438 filed Aug. 10, 1990, entitled LEAD STRAIGHTENING METHOD AND APPARATUS. The disclosure of this pending application is incorporated herein by reference in its entirety. In this pending patent application, apparatus is described and claimed which positions DIP devices of the type described herein at a lead straightening station, straightens the leads, moves the device to a coplanarity station and adjusts the positioning of the pads of the leads so that they are aligned in a common plane.
While the above described apparatus is efficient and effective, it is a waste of time to straighten or align the leads of a device which has one or more leads missing or when the leads are too far from acceptable standards. Such devices should be discarded. It is also unnecessary to subject already straightened DIP devices to additional straightening. Accordingly, it is a principal object of this invention to provide an inspection apparatus for use with the above described straightening apparatus which will reject defective DIP devices and pass acceptable DIP devices without requiring additional operation of the straightening or aligning apparatus.
Inspection devices per se are not new, of course. For example, coplanarity inspection of DIP devices has been described in a commonly owned copending Linker U.S. patent application Ser. No. 427,797, filed on Oct. 27, 1989. Another device is described in a continuation in part Linker et al. U.S. patent application Ser. No. 526,162, filed May 21, 1990, entitled COPLANARITY INSPECTION MACHINE. Both of these applications describing coplanarity inspection devices are incorporated herein by reference.
There are also various methods which are proposed for determining the relative alignment of the individual pins or leads of DIP devices. As can be determined from the very name of DIP devices, Dual In-Line Packages, the body portion of a DIP device has a plurality of leads extending from two sides generally perpendicular to the longitudinal axis of the device. Various devices have been proposed which scan the pin to pin relationship of the leads on DIP devices. Devices which pass the scanning test can then continue on in the manufacturing process while those which fail the test must be removed, either at the time of inspection or after the entire batch of devices has been scanned.
As one can imagine, there are alternative processes in the electronics industry. One such alternative is to straighten and position all of the leads on all of the devices prior to use. This is time consuming, expensive and potentially hazardous, particularly for fragile leads. The other alternative is to scan each individual lead and transfer those leads which need adjustment to the appropriate adjustment station. As a sufficient quantity of out of specification DIP devices accumulate, they can then be placed in a straightening device of the type described above. This may be suitable for small operations or operations which do not have an extremely high production rate. As more and more assembly facilities are being automated and the efficiencies of the automated plants are being upgraded, separation of the devices in this manner becomes non-productive or uneconomic.
The alternative to independently testing all of the leads and separating those which need straightening is the aforementioned process of straightening and aligning all of the leads. Even with virtually one hundred percent acceptance after straightening, these systems operate too slowly to be competitive in high volume assembly environments.
Accordingly, another object of the present invention is to provide a device which is capable of inspecting DIP device leads both from lead to lead distance, and for coplanarity, followed by selectively straightening those DIP devices which need adjustment to meet specification, even though that may be two percent or less of the total quantity processed. At the same time, it is an object of this invention to provide a machine which is capable of inspecting DIP devices for location and coplanarity alignment without subjecting those within specification to additional stress.
Yet another object of this invention is to provide a device which optimizes the inspection and adjustment of leads on DIP devices at a maximum rate with minimum stress on the device.
Other objects will appear hereinafter.